Field of the Invention
The invention relates to a controller and particularly relates to a DC-to-DC controller, a DC-to-DC power converter and a control method thereof.
Description of Related Art
FIG. 1A is a schematic view of a conventional DC-to-DC buck converter. In a typical buck converter 10, an error amplifier circuit 16 generates an error signal EA according to an output voltage Vout1 (or a feedback voltage related to the output voltage Vout1) and a reference voltage VRef. A time generation unit 14 generates a time signal STX1 according to the error signal EA, and, correspondingly to the time signal STX1, a driver 15 generates an upper-bridge control signal UG1 and a lower-bridge control signal LG1 to an output stage 11, so as to adjust the output voltage Vout1.
FIG. 1B is a schematic view of waveforms of a conventional output stage. When voltage identification (VID) of a central processing unit (CPU) changes, the related reference voltage VRef changes accordingly. When the VID changes from high to low, a conventional feedback control method is to continuously turn off an upper-bridge switch Q1 and turn on a lower-bridge switch Q2. A current is released via the lower-bridge switch Q2 to reduce the output voltage Vout1 until the output voltage Vout1 becomes equal to the reference voltage VRef. However, the continuous turn-on of the lower-bridge switch Q2 may cause a large negative current (not illustrated in FIG. 1B) on an output inductor L1 and cause undershoot in the output voltage Vout1, resulting in an unstable output. An excessively large negative current may even burn out the output inductor L1.